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Bladder NIRS: A non-invasive method functional to distinguish between detrusor underactivity (DU) and Bladder Outlet Obstruction (BOO) in men with LUTS

  • Romei L.,
  • Tuzzolo P.,
  • Civitella A.,
  • Prata F.,
  • Crimi V.,
  • Esperto F.,
  • Prof. Papalia R.,
  • Prof. Scarpa R.M.

Introduction & Objectives

The Bladder NIRS (Near infrared spectroscopy:NIRS) is a non-invasive diagnostic procedure to inquire into real-time the hemodynamic alterations (assessing oxy- and deoxyhemoglobin levels) during the bladder work, with the intention to connect them to specific illnesses. The final part of our research was to consider the skill of Bladder NIRS in to distinguish bladder outlet obstruction (BOO) from detrusor underactivity (DU). The results achieved by the Bladder NIRS have been compared to urodinamycs findings in the same patients.

Materials & Methods

From November 2019 to April 2021, 61 male patients aged between 55 and 80 years were selected, suffering from moderate-severe grade LUTS, subjected to a Bladder NIRS study and a pressure-flow study. Only patients with Qmax <15 ml/sec were selected for the study. NIRS detector was located orizontally at the midline, 2 cm on top of the pubic symphysis. We have determined, according to Nitti, the obstruction as the presence of a Schafer index >= 3. The concordance rate between the results obtained by PFS and NIRS-voiding phase relatively for discriminating the presence of BOO from DU was calculated using the “Kappa” Cohen index.


PFS established  the presence of DU in 28 cases , of these, 24 presented a flat NIRS pattern while PFS defined the presence of BOO in 33 cases, of these 26 presented a downward pattern.
The concordance rate for discriminating DU (flat nirs tracing) from BOO (tracing nirs downward) was “good” (K =0.64). We have found, in patients with Qmax less than 15 ml / sec, subjected to bladder nirs examination and to the pressure-flow study, a high correlation between the diagnosis of DU obtained at the pressure-flow study and the pattern nirs tracing “Flat”, that is to say the majority of patients with DU, presents values of concentration of oxyhemoglobin and deoxyhemoglobin with a difference of no more than -/+ 3 micromolar/sec.


PFS is currently the “gold standard” for the diagnosis of DU; however, for its invasiveness, this method is poorly tolerated with high costs and possible complications such as urinary tract infections, urethral and / or bladder iatrogenic injuries. The data obtained from our preliminary experience, according to the scientific literature, encourage to continue Bladder NIRS-voiding phase studies for high concordance rate with FPS. Our experience shows good correlation in discriminating patients with BCI ( bladder contractility index) lower to 100 with flat pattern in the definition of DU from patients BOO with a downward pattern (the concordance rate with the index “Kappa” Cohen is good, equal to 0.64).